Together with the 74 lines belonging to (0,9,0)(0,0,0) band, the high-resol
ution absorption spectrum of H2O+ (A) over tilde (2) A(1) - (X) over tilde
(2) B-1 system was observed in the visible region of 16680 - 17300 cm(-1) u
sing optical heterodyne magnetic rotation enhanced velocity modulation spec
troscopy for the first time, which verifies the high sensitivity and high s
ignal to noise ratio (S/N) of this technique.